Update the accessibility tree when a modal dialog is opened/closed.

Source/core/accessibility/AXObject.cpp

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 271 matching lines @@
         return IgnoreObject;
 
     if (isPresentationalChildOfAriaRole())
         return IgnoreObject;
 
     return accessibilityPlatformIncludesObject();
 }
 
 bool AXObject::isInertOrAriaHidden() const
 {
-    if (equalIgnoringCase(getAttribute(aria_hiddenAttr), "true"))
-        return true;
-    if (node() && node()->isInert())
-        return true;
-
-    for (AXObject* object = parentObject(); object; object = object->parentObject()) {
+    bool mightBeInInertSubtree = true;
+    for (const AXObject* object = this; object; object = object->parentObject()) {
         if (equalIgnoringCase(object->getAttribute(aria_hiddenAttr), "true"))
             return true;
+        if (mightBeInInertSubtree && object->node()) {
+            if (object->node()->isInert())
+                return true;
+            mightBeInInertSubtree = false;
+        }
     }
 
     return false;
 }
 
 bool AXObject::lastKnownIsIgnoredValue()
 {
     if (m_lastKnownIsIgnoredValue == DefaultBehavior)
         m_lastKnownIsIgnoredValue = accessibilityIsIgnored() ? IgnoreObject : IncludeObject;
 
@@ skipping 587 matching lines @@
         return ToggleButtonRole;
     if (ariaHasPopup())
         return PopUpButtonRole;
     // We don't contemplate RadioButtonRole, as it depends on the input
     // type.
 
     return ButtonRole;
 }
 
 } // namespace WebCore